Many types of devices have been developed over the years for the purpose of converting liquids or aerosols into gas-phase fluids. Many such devices have been developed, for example, to prepare fuel for use in internal combustion engines. To optimize fuel oxidation within an engine's combustion chamber, the fuel/air mixture commonly must be further vaporized or homogenized to achieve a chemically-stoichiometric gas-phase mixture. Ideal fuel oxidation results in more complete combustion and lower pollution.
More specifically, relative to internal combustion engines, stoichiometricity is a condition where the amount of oxygen required to completely burn a given amount of fuel is supplied in a homogeneous mixture resulting in optimally correct combustion with no residues remaining from incomplete or inefficient oxidation. Ideally, the fuel should be completely vaporized, intermixed with air, and homogenized prior to entering the combustion chamber for proper oxidation. Non-vaporized fuel droplets generally do not ignite and combust completely in conventional internal and external combustion engines, which presents problems relating to fuel efficiency and pollution.
Incomplete or inefficient oxidation of fuel causes exhaustion of residues from the internal or external combustion engine as pollutants, such as unburned hydrocarbons, carbon monoxide, and aldehydes, with accompanying production of oxides of nitrogen. To meet emission standards, these residues must be dealt with, typically requiring further treatment in a catalytic converter or a scrubber. Such treatment of these residues results in additional fuel costs to operate the catalytic converter or scrubber. Accordingly, any reduction in residues resulting from incomplete combustion would be economically and environmentally beneficial.
Aside from the problems discussed above, a fuel-air mixture that is not completely vaporized and chemically stoichiometric causes the combustion engine to perform at less than peak efficiency. A smaller portion of the fuel's chemical energy is converted to mechanical energy when fuel is not completely combusted. Fuel energy is wasted and unnecessary pollution is created. Thus, by further breaking down and more completely vaporizing the fuel-air mixture, better fuel efficiency may be available.
Many attempts have been made to alleviate the above-described problems with respect to fuel vaporization and incomplete fuel combustion. In automobile engines, for example, direct fuel injection has almost universally replaced carburetion for fuel delivery. Fuel injectors spray a somewhat fine fuel mist directly into the cylinder of the engine and are controlled electronically. Currently, it is believed by most that the fuel injector spray allows the fuel and air to mix in the cylinders more efficiently than carburetion. Nevertheless, the fuel droplet size of a fuel injector spray is not optimal and there is little time for the fuel to mix with air prior to ignition. Even current fuel injector systems do not fully mix the fuel with the necessary air.
Moreover, it has been recently discovered that fuel injector sprays are accompanied by a shockwave in the fuel spray. The shockwave may prevent the fuel from fully mixing with air. The shockwave appears to limit fuel mass to certain areas of the piston, limiting the fuel droplets' access to air.
Other prior systems have also been developed in attempts to remedy the problems related to fuel vaporization and incomplete fuel combustion. For example, U.S. Pat. Nos. 4,515,734, 4,568,500, 5,512,216, 5,472,645, and 5,672,187 disclose various fuel vaporizing devices.
Nevertheless, prior vaporization devices fail to provide a configuration which is large enough to attain volumetric efficiencies at high RPM's, yet small enough to get high resolution responses at lower RPM's. Indeed, the prior devices have generally had to choose between volumetric efficiency at high RPM's and high resolution response at lower RPM's.